I've bought the annual pass every year for about 6 years, even if we weren't planning to go to one of the big 63 we'd use it at other places park areas or just have it to support the parks ab it.
With Trump putting his face on it I planned to pay the entry fee at each of the 7 parks we're planning to visit this year. I can budget for it and it helps the parks.
We were at Indiana Dunes getting a brochure and the ranger tried to sell me the annual pass and then asked if I was a veteran. That reminded me to ask about the access pass. I read online that you have to have forms signed by a doctor, the ranger said Nope, just sign this testifying that you have a permanent disability.
I've had celiac disease for 8 years now, turns out that ranger does too and assured me it was a covered disability. So now I have a free lifetime pass with an owl on it instead of a pedophile.
Our friend camping with us has MS and I told her about me getting the pass, she walked up to the ranger and said "I have MS", he said "I got ya" and pulled the form back up.
So, if you're thinking about the access pass don't worry about all the paperwork they require online. Just visit your local ranger and talk to them. Though, your mileage may vary if you get a stickler, but both people working the desk said they didn't want to know about my medical history and were happy to help me out.